![Air monitoring measurement system by [Sound]](images/h3_pdt5_dl8.gif){kind=small}
The flight path measurement system consists of two or more flight path measurement stations (DL-90/C) and the central station. Each DL-90/C continuously monitors the arrival direction vector of the noise that an aircraft produce and transfer vector data to the central station. At the central station, the host PC processes those data according to the principle of triangulation, then produces the three-dimensional flight paths of aircrafts throughout the year.
Because the impact of aircraft noise changes so widely according to the type of aircraft, the weather condition and the flight path, understanding both the trail and the noise has been an important problem for the noise administration.
Although in some civil airports, they have opened their radar flight path to the public and it has been used to watch for the deviation of the flight paths, the purpose or the extent to use the data has been limited and it is difficult to use as information for administrative countermeasure against noise. Moreover, since it is difficult to expect a military airport to open up their radar information in the future, we are convinced that the demand for a continuous annual measurement of flight paths will continue to increase.
Now, a flight path monitoring station has been established in 5 locations along the extended line of runway A on the north side of Narita international Airport to measure the continuous three-dimensional flight paths of the aircrafts taking off and landing on runway A and the aircrafts that fly to the north side of the airport.
This system began to be used from April 2001, and has carried out the measurement in the area that is 4km-10km north from the north end of runway A, in precision of about plus or minus 50m and the acquisition rate of more than 96%. Since the accumulation of the data has advanced making it possible to grasp the connection between the sound pressure level and the aircraft's coordinates more clearly, we are considering that predicting the noise distribution around the airport will be possible in the near future.
